It is necessary when you are getting into multiplying from the outside of parenthesis and multiplying variables inside of parenthesis.
ex: 5(3 + 3x)
5 * 3 = 15
5 * 3x = 15x
so final set up would be 15 + 15x
I'm new too, but I'm pretty sure if you have a question then you ask it, attach a picture if needed, and people might see it and answer.
Answer:
slope is -1/4
Step-by-step explanation:
=
= 
and so on...
formula: 
hope this helps!!!
Answer:
1600/49
Step-by-step explanation:
5 5/7 = 40/7
40/7 * 40/7 = 1600/49